Apparatus for handling coke oven doors



Feb. 21, 1961 s. s. STONE APPARATUS FOR HANDLING COKE OVEN oooas 6 Sheets-Sheet 1 Filed Jan. 2, 1958 1N VENTOR SELDEN S. STON E ATTORNEYS Feb. 21, 1961 s. s. STONE APPARATUS FOR HANDLING COKE OVEN DOORS 6 Sheets-Sheet 2 Filed Jan. 2, 1958 INVENTOR SELDEN S. STONE ATTORNEYS Feb. 21, 1961 s. s. STONE APPARATUS FOR HANDLING coma: OVEN DOORS 6 Sheets-Sheet 3 Filed Jan. 2, 1958 INVENTOR SELDEN s. STONE ATTORNEY S s. s. STONE APPARATUS FOR HANDLING coxs OVEN DOORS Feb. 21, 1961 6 Sheets-Sheet 5 Filed Jan. 2, 1958 INVENT OR SELDEN S. STONE ATTORNEYS Feb. 21, 1961 s. s. STONE 2,972,422

APPARATUS FOR HANDLING COKE: OVEN DOORS Filed Jan. 2, 1958 6 Sheets-Sheet 6 CARRIAGE DRIVE I Q m it ii||| j 3 il a a H l I I w E 5 g E 3 z i: s

i i J F i J INVENTOR L semen s. STONE ATTORNEYS United States Patent TO 2,972,422 APPARATUS non HANDLING COKE OVEN DOORS Selden 5. Stone, Weirton, W. Va., assignor to National Steel Corporation, a corporation of Delaware 'Filed Jan. 2, 1958, Ser. No. 706,685

11 Claims. (Cl. 212-4) The present invention relates to apparatus for handling coke oven doors, and more particularly to such apparatus having means for assuring alignment with the door to be handled.

In the production of coke in by-prod'uct coke ovens, it is customary to provide a battery of ovens side-byside. These ovens are rather long from front to rear and each is of a height several times its width. The front of each oven is provided with a narrow, vertically elongated door. The doors of the battery are aligned and lie in a common plane. Support for the forward ends of the ovens is afforded by a plurality of buckstays such as verticallydisposed l-beams one between each pair of adjacent doors with the plane of the doors a little to the rear of the front of the buckstays.

The front of the door jamb of each oven is conventionally provided with releasable latches for securing a door in closed position. The door, in turn, is provided with a resilient peripheral sealing metal gasket adapted sealingly to contact the door jamb to reduce loss of coke oven gases. These flanges are known in the art as seal ing rings.

During the coking operations, it is necessary to remove the door at the end of the coking period to insert a pusher member into the oven to eject coke to the rear. Thereafter, the door is replaced in sealedrelationship. Machines have heretofore been developed to perform the combined operations of door removal, coke pushing and door replacement. conventionally, these machines have a pair of extensible and retractable booms disposed side-by-side and movable relative to their car-- riage in parallelism with each other. One boom has mechanism at its outer end which engages with and retracts the oven door and usually sets and releases the door latches. The other boom is a pusher boom for ejecting coke to the rear of the oven. The operator of the machine rides in a cab which is in line withcthe pusher boom so that the operator can see into the oven and accurately control the ejecting operation. Thus the door handling boom is disposed to one side of the operators forward line of sight.

A single machine services an entire battery of ovens. To this end, the machine is mounted on tracks which are parallel to and in front of the line of oven doors.

The machine is movable on the tracks in a path parallel to the doors and the boomsare extensible toward and retractable away from the doors along lines which are perpendicular to the plane of the doors.

To service a particular oven, the operator moves the machine along the tracks until it is roughly in front of the oven in question. He must position the machine so the door handling boom is aligned with boom engaging elements on the oven door. He extends this boom to engage with the door elements and retracts the boom to remove the door with the door supported on the end of the boom. Then he moves the machine along the tracks a distance equal to the distance between the two booms and in a direction such that the pusher boom is ous problem.

r ice now aligned with the open oven. He extends the pusher boom, performs the pushing operation and retracts the pusher boom. A man or machine cleans the door jamb. The operator then returns the carriage to the first position, extends the door handling boom and replaces the door.

As noted above, the door handling boom is off to the side of the operatorsline of sight, andhe has difiiculty replacing the door accurately. He must fit the door neatly onto the jamb between the forwardly extending buckstays and between the door latches. If his alignment is inaccurate he will strike these projecting parts with the door. The sealing ring of the door is peripherally disposed and will be damaged. These sealing rings are made of high alloy steel or stainless steel, are extensive and are machined and fitted with great precision so as to seal securely. They are quite expensive and it is a costly and time consuming procedure to replace or repair them.

In the past, damage to scaling rings resulting from misalignment when replacing oven doors has been a seri- It would be no solution to this problem to align the operators cab with the door handlingboom, for then the operator could not see into the oven and sight along the pusher boom and could not accurately control the pushing operation. Nor could the two booms be vertically superposed for simultaneous alignment of both, since the extracted door on a door handling boom would interfere with operation of the pusher boom.

The present invention overcomes these difiiculties of the prior art by providing, in connection with a conventional pusher and door machine, reciprocable indicator means movable in the manner of a third boom to an extended position for alignment with fixed target means contiguous to a coke oven. Additionally, means are 7 provided operable to move the door handling means toward the oven only when the reciprocable indicator means is extended. In this way, the operator cannot remove or replace a door until he has first extended the indicator means, so that he cannot forget orignore the indicator means. When the indicator means is aligned with the fixed target means contiguous to an oven, the door handling boom will be aligned with an oven door. Accordingly, as a refinement, it is provided that the door handling boom be extensible onlywhen the indicator means is both'extended toward and aligned with the fixed target means contiguous to an oven.

It is also customary in coke oven practice to provide a platform along the front of a battery of ovens between the ovens and the tracks of the pusher and door machine. This platform is raised from the level of the tracks and is disposed only a little below the bottom of the doors. It is known in the art as a bench and serves as a support for a number of work operations in connection with the cleaning and repair of the ovens and their doors.

a For example, men equipped with cleaning bars work on the bench cleaning tarry residue from furnace walls. The bench also supports ladders on which workmen stand while greasing the doors. Cleaning machines ride on the bench for cleaning tarry residue from the oven door jambs and inner side of extracted doors. The cracks which develop in the refractory materials around the doors are patched with powdered material dispensed from blowers known in this art as heaters, and these heaters are also supported on the bench.

Thus, the bench is often a busy and cluttered place, and it would obviously be destructive or even dangerous to move a machine according to the present invention along the tracks with the indicator means extended; It might .at first seem that the operator would naturally retract the indicator means when he retracts either of the other two booms, but such is not necessarilythe case. He has no choice but to retract the door handling boom as he cannot disengage from the door and clear the buckstays until he does. Similarly, he obviously must withdraw the pusher boom from the furnace before he can move the machine along the tracks. But no such physical limitations force him to retract the indicator means. Indeed, the indicator means performs no actual work operation on the oven or its door so that he is even more likely to forget or neglect to retract it between work operations.

Accordingly, the present invention also provides means preventing movement of the machine bodily along the tracks until the indicator means is retracted. In. the illustrated embodiments, this means comprises means operable to move the door handling means away from the ovens only when the indicator means is retracted.

Thus, in its illustrated embodiments, the present invention provides that a movement ofv the door handling means in either direction must be preceded by a corresponding movement of the indicator means. This arrangement has the double advantage of assuring that the door handling means will be aligned with the oven and that the indicator means will be retracted between work operations.

Other objects and advantages of the present invention will become apparent fro-m a consideration of the following description, taken in conjunction with the accom panying drawings, in which:

Figure 1 is a fragmentary side elevational view of apparatus according to the present invention in its operative environment, with parts broken away and parts shown in section; V

Figure 2 is a plan view of the structure shown in Figure 1;

Figure 3 is a diagrammatic view of the indicator means and door handling means and their controls, with parts indicated by conventional symbols;

Figure 4 is a View similar to Figure 3 but showing a modified form of the invention;

Figure 5 is a view similar to Figure 3 but showing a further modified form of the invention; and

Figure 6 is a view similar to Figure 3 but showing a still further modified form of the invention.

Referring now to the drawings in greater detail, there is shown a battery of by-product coke ovens indicated generally at It) and comprising a plurality of. ovens 12 disposed in side-by-side relationship. Each, oven 12 is rather long from front to rear and of a height several times its width. Support for the forward ends of the ovens is afliorded by a plurality of buckstays 14 which in the illustrated embodiment are vertically disposed I-beams one between each pair of adjacent ovens 12. Each oven is provided at its front with a narrow, vertically elongated door 16. The doors of the battery are aligned and lie in a common plane disposed somewhat to the rear of the front of the buckstays. The doors and their associated door jambs are provided with conventional coacting latch mechanisms 18 for releasably securing the doors in closed position. In addition, each door is provided with a plurality of vertically spaced hook plates 20 for supporting the door during removal and replacement.

A pusher and door machine modified according to the present invention is indicated generally at 22 and is supported for movement parallel to the line of doors 16 on tracks 2 of which only the one nearer the ovens is shown. Tracks 24 are parallel to and spaced in front of and below the line of doors 16. Wheels 26 provide rolling support for machine 22 on tracks 24 and these wheels are driven through drive shafts 28 by means of conventional motors (not shown) so that machine 22 may be driven any suitable distance in either direction along tracks 24 thereby to service any of ovens 12.

A bench 30 for. the support. ofv the. Work operations described above is provided along the front of ovens 12 between the ovens and tracks 24. Bench 30 is raised from the level of tracks 24 and is disposed only a little below the bottoms of doors 16.

Machine 22 is provided with the usual pusher boom 32 selectively reciprocable by reversing means (not shown) toward and into and away from ovens 12 under the control of an operator sitting in the operators cab 33. As is also conventional, cab 33 in effect straddles boom 32 so that the operator can sight along boom 32 to control the discharge of coke to the rear of the ovens at the end of the coking process. Machine 22 is also provided with a conventional reciprocable leveling boom 34 for leveling the charge in the ovens.

Also mounted on machine 22 for reciprocation toward and away from the ovens is door handling means comprising a door handling boom 36 which is extensible under the influence of forward motor 38 and retractable under the influence of reverse motor 4d. At its outer or door engaging end, door handling boom 36 is provided with the usual latch releasing and door supporting mechanisms 42 including door hooks 44 for engaging under hook plates Zn on doors 16 to support the doors during removal and replacement.

The structure and coaction of the door handling boom and the doors and their sealing rings are conventional and representative structures of thistype are to be found in United States Patents Nos. 2,123,521, 2,576,126 and 2,746,610. Moreover, it will be understood that the provision of pusher boom 32, leveling boom 34 and door handling boom 36 for reciprocation selectively along lines parallel to each other and perpendicular to the plane of doors 16 is also conventional and as such forms no part of the present invention.

A very important feature of the present invention is the provision of indicator means indicated generally at 46 comprising a fluid pressure motor having a fluid pressure cylinder 48 disposed perpendicular to the plane of doors 16 and secured on the oven side of machine 22 by a bracket 50. As seen for example in Figure 3, means 46 includes an indicator boom 52 comprising a doubleended piston rod having a piston 54- secured intermediate the ends thereof for axial slidin movement within cylinder 48. Pressure fluid is supplied to and discharged from opposite ends of cylinder 48 by conduits 56 and 58.

The supply and discharge of pressure fluid is controlled by a distributing valve on having a double-ended spool 62 extending axially t-herethrough. A pair. of spaced pistons 64 is mounted on spool 62 for separating the fluid channels in various operative positions of valve 60. Pressure fluid is supplied through feed conduit 66 from a source of pressure fluid (not shown), and pressure fluid is returned or vented through return conduits 68 and 70.

Valve 60 at rest is biased to the neutral. position shown in Figures 3 and 4 by means of coil. compression springs 72 acting against abutments 74. In this position, conduits 56, 58, 66, 68 and 70 are all cut off from each other and indicator means 46 is necessarily at rest. However, provision for moving the indicator boom 52 in either direction is made by means of moving spool 62 to one of two operative positions under the influence of solenoid coils 76 or 72. Specifically, the closing of normally open switch S-l actuates coil '76 to urge spool 62 to the right as seen in Figure 3 against the action of the adjacent spring 72. This movement places conduits 66 and 53 in fluid circuit with each other to supply pressure fluid tothe right end of cylinder 48 as seen in Figure 3 to move indicator boom 52 to the left as seen in Figure 3. At the same time, conduits 56 and 63 are placed in fluid circuit and conduit 7%? is cut off so that the fluid in the left end of cylinder as as seen in Figure 3 discharges through conduits 56 and 68. When released, switch 54 returns to open position and valve 50 resumes the position shown in Figure 3, whereupon movement of boom 5 52-stops. Similarly, upon the closing of normally open switch S-2, solenoid coil 78 is actuated to urge spool 62 to the left as seen in Figure '3 so that pressure fluid passes from conduit 66 through conduit 56 tomove boom 52 to the right as seenin Figure 3, while fluid discharge occurs through the circuit of conduits 58 and 70 and conduit 68 is cut E. v i

At the forward or oven end of boom 52 is a pointer 80 alignable with a fixed target 82 contiguous to ovens 12. Specifically, a target 82 is mountedon the front of each of buckstays 14. As best seen in Figure 2, the distance between each target 82'and the center line of the oven to which it pertains is the same as the distance between indicator boomt52 and door handling boom 36 when viewed from above. Thus, when pointer 80 and target 82 are aligned, door handling boom 36 will be properly aligned with an oven door 16. It should be noted that each target 82 is not necessarily adjacent the oven to which pertains, and in the illustrated embodiment it is spaced from that oven by an intermediate oven. In otherwords, the horizontal distance between booms 36 and 52 will always be an even multiple of the horizontal distance between furnace center lines (including zero) .plus half the distance between furnace center lines when targets 82 are centered on buckstays 14 asshown. This relationship will hold true throughout the length of the line of ovens 12, since boom 52 moves in parallelism with boom 36. 7

Another very important feature of the present invention is the interconnection of the controls of booms. 36 and 52. Boom 52 at its end opposite pointer 80 is provided with a double surfaced cam 84 which inthe extreme extended position of boom 82 contacts and closes normally open limit switch LS-1 and in the extreme retracted position of boom 52 contacts and closes normally open limit .switch LS-Z. -LS-1 is in series with forward motor 38 for extending the door handling boom 36,a.source of electric power E-l for. driving motor 38, a normally closed limit switch LS-3 and a normally open selectively operable switch 8-3. Regardless of whether switch 5-3 is held closed, the circuit of motor 38 will be broken until LS-1 is closed, and the only instrumentality for. doing this is cam 84,when boom 52 is in extended position. Thus, door handling boom 36 cannot be moved forward until boom 52 is extended. 7

Similarly, LS-2 iSli11 series with reverse motor 40 for moving door handling boom 36 to a retracted position, a source of electricpower E-2 for driving motor 40,

a ,fixed target, since the target does not move until contacted by pointer 80' andhence for target purposes is fixed. 7 m I It will also be understood that it is within the com .templation of the present invention that the means for moving machine 22 along tracks 24 be operable only whenindicator boom 52 is in its retracted position,

regardlessv of whether retraction of boom-52 precedes or follows retraction of door handling boom 36. Thus,

it is also within the scope of the present invention that LS-2 be in circuit with the motors for moving machine 22 along tracks 24 rather than in circuit with reverse motor 40, as shown in Figures 5 and 6.

The operation of the present invention is. as follows:

The operator in cab 33 moves machine 22 along tracks 24 until door handling boom 36 is approximately opposite the oven to be serviced. Indicator boom 52 is retracted during this movement and when machine 22 comes to rest the operator closes switch 8-1 to extend boom 52. He then makes a fine adjustment of the posi- 7 tion of machine 22 along tracks 24 until pointer 80 is aligned with fixed target 82 in the embodiment of Figure 3 or LS-l in the embodiment of Figure 4. In either case, the circuit of forward motor 38 of door handling boom 36 may now be closed by closing switch 8-3 to extend boom 36 to engage and unlatch oven door 16 in the conventional way. Indicator boom 52 is then retracted to close LS-2 so that upon the closing of switch S-4 boom 36 carrying door 16 may be retracted by operation of reverse motor 40.

"With booms 36 and 52 retracted, the operator then moves machine 22 along tracks 24 a distance equal to the horizontal distance between boom .36 and pusher boom 32 in" a direction such that pusher boom 32 is a normally closedlimit switch LS-4 and a normally open selectively operable switch 8-4, so' that the closing of S- -4 will be effective to actuate motor 40 to return boom 36 only when cam 84 contacts and closes,LS-2,

that is, when indicator boom 52 is retracted.

Selectively operable switches 8-1, 8-2, 8-3 and 5-4 I are conveniently located in the operators cab 33.

Limit switches LS-3 and LS-4 are opened by cam 86 for the location and actuation of LS-l. In Figure 4,

LS-l is so positioned that it performs the functionsof both target 82 and LS1 of Figure 3. In Figure'f4, -LS-1 islnolonger actuated by cam 84 but by pointer 80.

- Thus, it is actuated not just when indicator boom 52 is extended, as in Figure 3,'but also only when pointer 80 -is extended and aligned with LS-1, for it is pointer 80 that actuates LS-l. In the embodiment ofFigure 4, LS-1 replaces targets 82 on buckstays 14 and becomes the fixed target means of this invention. The fact that LS-1 has a movable switch-actuating member moved uponcontact with pointer '80 does not alter its nature as ing a selectivelymovable carriage, coke oven door sup- 7 aligned with the open oven 12. This alignment isrelatively easy, since the operator can sight along' pusher boom 32. He then extendspusher boom 32 into the oven to discharge coke from the rear thereof in the usual way and retracts the pusher boom. Thereafter, he moves machine 22 back along tracks 24 to the position first described and'repeats the extension and alignment of the'indicator means with the fixed target means followed by the extension of door handling boom 36, as described above, to replace the door 16 in nice alignment without injuring any portion of the door. Finally, booms 52 and 36 are again retracted in that order and machine 22 is ready to move on to service another illustrated in connection with preferred embodiments, it

is to be-understood that modifications and variations may be resorted to Without departing from the scope of this invention, asthose skilled in this art'will readily appreciate. Such modifications and variations are considered to be within the purview and scope of the present invention as defined by the appended claims.

What is claimed is: M i r -,'1. Apparatus for handling coke oven doors, comprisporting means mounted on the carriage for movement relative to the carriage away from the carriageon one side of the carriage to emplace a coke oven 'door, indi'- cator means mounted on the carriage for movement relative to the carriage away fromthe carriage on said one side of the-carriage, means for efiecting said movement of the indicator means to an extended position to enable alignment ofthe indicator means with fixed tar get means contiguous' to a coke oven by movement of the carriage, and means operable only when the indiside of the carriage to emplace a coke oven door, indi cator means mounted on the, carriage for movement relative to the carriage away from the carriage on said one side of the carriage, means for eiiecting said movement of the indicator means to an extended position to enable alignment of the indicator means with fixed target means contiguous to a coke oven by movement of the carriage, and means operable only when the indicator means is in an extended position and aligned with the fixed target means contiguous to a coke oven for eifecting said movement of the coke oven door supporting means.

3. Apparatus for handling coke oven doors, comprising a selectively movable carriage, coke oven door supporting means mounted on the carriage for reciprocatory movement relative to the carriage away from and toward the carriage on one side of the carriage to emplace a coke oven door and to return, indicator means mounted on the carriage for reciprocatory movement relative to the carriage away fromand toward the carriage on said one side of the carriage, means for efiecting said movement of the indicator means away from the carriage to an extended position to enable alignment of the indicator means with fixed target means con tiguous to a coke oven by movement of the carriage and for efiecting said movement of the indicator means toward the carriage to a retracted position, means operable only when the indicator means is in an extended position for efiecting said movement of the coke oven door supporting means away from the carriage, and means operable only when the indicator means is in a retracted position for efi'ecting said movement of the coke oven door supporting means toward the carriage.

4. Apparatus for handling coke oven doors, comprisiug a selectively movable carriage, coke oven door supporting means mounted on the carriage for reciprocatory movement relative to the carriage away from and toward the carriage on one side of the carriage to emplace a coke oven door and to return, indicator means mount ed on the carriage'for reciprocatory movement relative to the carriage away from and toward the carriage on said one side of the carriage, means for effecting said movement of the indicator means away from the carriage to an extended position to enable alignment of the indicator means with fixed target means contiguous to a coke oven by movement of the carriage and for effecting said movement of the indicator means toward the carriage to a retracted position, means operable only when the indicator means is in an extended position and aligned with the fixed target means contiguous toa coke oven for effecting said movement of the coke oven door supporting means away from the carriage, and means operable only when the indicator means is in a retracted position for effecting said movement of the coke oven door supporting means toward the carriage.

5. In a battery of by-product coke ovens having a plurality of aligned door jambs, track meansadiacent and parallel to the line of door jambs, a carriage supported on the track means for movement parallel to the line of door jambs, and coke oven door supporting means mounted on the carriage for movement relative to the carriage toward the ovens to emplace a coke oven door on a coke oven door jamb, the combination comprising indicator means mounted on the carriage for movement relative to the carriage toward the ovens, fixed target means contiguous to the ovens, and means for effecting said movement of the indicator means to an extended position to enable alignment of the indicator means and fixed target means with each other by movement of the carriage.

6. In a battery of by-product coke ovens having a plurality of aligned door jambs, track means adjacent and parallel to the line of door jambs, a carriage supported on the track means for movement parallel to the line of door jambs, and coke ovendoor supporting means mounted on the carriage for movement relative to the carriage toward the ovens to emplace a coke oven door on a coke oven door jamb, the combination comprising indicator means mounted on the carriage for movement relative to the carriage toward the ovens, fixed target means contiguous to the ovens, means for effecting said movement of the indicator means to an extended position to enable alignment of the indicator means and target means with each other by movement of the carriage, and means operable only when the indicator means isin an extended position for elfecting said movement of the coke oven door supporting means.

7. In a battery of by-product coke ovens having a plurality of aligned door jambs, track means adjacent and parallel to the line of door jambs, a carriage supported on the track means for movement parallel to the line of door jambs, and coke oven door supporting means mounted on the carriage for movement relative to the carriage toward the ovens to emplace a coke oven door on a coke oven door jamb, the combination comprising indicator means mounted on the carriage for movement relative to the carriage toward the ovens, fixed target means contiguous to the ovens, means for effecting said movement of the indicator means to an extended position to enable alignment of the indicator means and target means with each other by movement of the carriage, and means operable only when the indicator means is in an extended position and the indicator means and target means are aligned with each other for effecting said movement of the coke oven door supporting means.

8. In a battery of by-product coke ovens having a plurality of aligned door jambs, track means adjacent and parallel to the line of door jambs, a carriage supported on the track means for movement parallel to the line of door jambs, and coke oven door supporting means mounted on the carriage for reciprocatory movement relative to the carriage toward and away from the ovens to emplace a coke oven door on a coke oven door jamb and to return, the combination comprising indicator means mounted on the carriage for reciprocatory movement relative to thecarriage toward and away from the ovens, fixed target means contiguous to the ovens, means for elfecting said movement of the indicator means toward the ovens to an extended position to enable alignment of the indicator means and target means with each other by movement of the carriage and for eifecting said movement of the indicator means away from the ovens to a retracted position, means operable only when the indicator means is in an extended position for effecting said movement of the coke oven door supporting means toward the ovens, and means operable only when the indicator means is in a retracted position for eifecting said movement of the carriage along the tracks.

9. In a battery of lay-product coke ovens having a plurality of aligned door jarnbs, track means, adjacent and parallel to the line of door giambs, a carriage supported on the track means for movement parallel to the line of door jambs, and coke oven door supporting means mounted on the carriage for reciprocatory movement relative to the carriage toward and awayv from the ovens to emplace a coke oven door on a coke oven door jamb and to return, the combination comprising indicator means mounted on the carriage for reciprocatory movement relative to the carriage toward and away from the ovens,-

iixed target means contiguous to the ovens, means for effecting said movement of the indicator means toward the ovens to an extended position to enable alignment of the indicator means and target means. with each other by movement of the carriage and for effecting said movement of the indicator means away from the ovens to a retracted position, means operable only when the indicator means is in an extended position for effecting said movement of the coke oven door supporting means toward the ovens, and means operable only when the indicator means is in a retracted position for effecting said aeviaaaa movement of the coke oven door supporting means away from the ovens.

10. In a battery of by-product coke ovens having a plurality of aligned door jambs, track-means adjacent and parallel to the line of door jambs, a carriage supported on the track means for movement parallel to the line of door jambs, and coke oven door supporting means mounted on the carriage for reciprocatory movement relative to the carriage towardand away from the ovens to emplace'a coke oven door on a coke oven door jamb and to return, the combination comprising indicator means mounted on the carriage for reciprocatory movement relative to the carriage toward and away from the ovens, fixed target means contiguous to the ovens, means for effecting said movement of the indicator means toward the ovens to an extended position to enable alignment of the indicator means and fixed target means with each other by movement of the carriage and for efiecting said movement of the indicator means away from the ovens to a retracted position, means operable only when the indicator means is in an extended position and the indicator means and target means are aligned with each other for effecting said movement of the coke oven door supporting means toward the ovens, andmeans operable only when the indicator means is in a retracted position for eifecting said movement of the carriage along the tracks.

11. In a battery of by-product coke ovens having a plu rality of aligned door jambs, track means adjacent and parallel to the line of door jambs, a carriage supported on the track means for movement parallel to the line of door iambs, and coke oven door supporting means mounted on the carriage for reciprocatory movement relative to the carriage toward and away from the ovens to emplace a coke oven door on a coke oven door jamb and to return, the combination comprising indicator means mounted on the carriage 'for reciprocatory movement relative to the carriage toward and away from the ovens, fixed target means contiguous to the ovens, means for effecting said movement of the indicator means toward the battery of ovens to an extended position to enable alignment of the indicator means and target means with each other by movement of the carriage and for elfecting said movement of the indicator means away from the ovens to a retracted position, means operable only when the indicator means is in an extended position and the indicator means and target means are aligned with each other for eliecting said movement of the coke oven door supporting means toward the ovens, and means operable only when the indicator means is in a retracted position for effecting said movement of the coke oven door supporting means away from the ovens.

References Cited in the file of this patent UNITED STATES PATENTS 1,357,058 Hubbell Oct. 26, 1920 2,252,807 Haberle Aug. 19, 1941 2,340,910 Truesdale Feb. 8, 1944 

